Circuit for electric discharge devices



April 18, 1933. J 1 REYNOLDS 1,904,533

CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Filed Dec. 51, 1929 2 Sheets-Sheet 1 i A T 3 i 57 Fl /-A S 70 G 75 L I A C p 8 FIG. /'8 L -//\/VEN7'O/P C 0 JLPe'Y/vows ATTOPNE) Patented Apr. 18, 1933 UNITED STATES JOHN L. REYNOLDS, or JACKSON HE HTS, NEW YORK, Assrenon T ELECTRIC L RESEARCH rmnuc'rs INC, or NEW. YORK, n. Y., A CORPORATION OF DELAWARE CIRCUIT non ELECTRIC DISCHARGE DEVICES Application filed December 31, 1929. Serial No. 417,640.

nection fromv the rid to the mid-point ofv I the secondary win ing of the filament energizing transformer, or to the mid-point of a potentiometer across this winding, will make the .average potential differences between cathode and grid substantially independent of the potential applied to the cathode. It

26 is also well known in the art that the anode or plate circuit is also connected to this midpoint tap, the same effect is obtained with respect to the anode circuit. Connections of this type may be found for exam le, in

"212 U. s. Patent 1,432,022, issued a) R. A, Heis ing Qctober 17 1922 and U. S. Patent 1387 $51, issued to J Farrington March 18, 1924. The effects of the fu damental a1 ternatingpotential Componenti'n the filament heating circuits on the current in the output circuit have been substantially eliminated by the use of this type of Connection.

further object of this invention is to eliminate or reduce the effect upon the plate or output current of the Circuit of variations in the filament supply current by balancing out or neutralizing the hum components produced by the filament supply current by their application to grid and anode circuits of tubes connected in phase opposition.

A feature of this invention is the use of a plurality of amplifying devices connected either in series oi'in parallel in a manner such that thehum'components produced by 43 the filament supply current in the output of one ofthe amplifying devices will be 180 out of phase with the hum Components produced by the filament current in the output of another of the amplifying devices and the resultant hum components transmitted to the load circuits amplitude.

j Another'feature of this invention is the use of a filament heating transformer having a plurality, of. secondary"windings each di: rectly connected to the series. connection of the filaments of a plurality oftubes'. p

An advantage ofthe circuit of'ithis inventron is the elimination'of the necessity of simulating the mid-point connection of the transformer to the filament. v

Other features and advantages of the in;

vention will be brought out and madempre fully apparent in the following"idescr-iptionf;; n connection with the' accompanying draw ngs in which: Fig. l is a s'chematicdraw mg of an amplifier comprising two push-' pull amplifiers in parallel witheach other, the filaments of the two tubes in each push.- .t pull amplifier being connected in series to separate windings of a filament heating transformer Figs. 1A'and' 1,Bare mod ifications of Fig. 1 in which the inputs to and the outputs from thetwo push' pull am} plifiers are connected inseries to theinpu't and output circuits respectively; Fig." 2 is a schematic drawing of a push-pull ampli fier employing four tubesparranged in pairs, each pair having its input and output electrodes connected in parallel, and the fila-l so Inent of one tube of each'pair connectedin series with one tube of the other pair and to a separate winding of. afilament heating transformer,.and Fig. '3 is an arrangement r51 similar to Fig. 2 except that the filaments "of 8 each pair of tubes are connected in series and to. a separate winding of the filament heating will at all'timesapproach zero 1 transformer.

Referring toFig. 1,.two push-pull ampli 6 fiers 1 and 2 comprise the repeating or: amplifying apparatusand these two amplifiers .ha-ve'the primary windings'3 and 4 of their respective input transformers or repeating coils 5 and 6 connected in parallel to the volt- 9'5 age source S by means of conductors 11 and 13 and 12 and 14 respectively. ThesourceS may comprise a detecton'anamplifierj or any othersuitable'source of varying potential, such as waves representing'speech, music'o'r 9 the like, which is to be amplified by the re peating apparatus.

The secondary winding of the transformer or repeating coil 5 is divided into two coils 7 and 9. Two electron discharge devices and 17 are included in the amplifier circuit 1. The electron discharge device15 comprises a heated filament or cathode 19, the anode or plate 21 and the control electrode or grid 23,

and the electron discharge device 17 c'om-' prisesthe heated filament or cathode 25, the anode or plate 27 and the control electrode 7 rent waves incoming from the source S by or grid 29.

Two electron discharge devices 16 and 18 are included inthe amplifier circuit 2. These electrondischarge devices 16 and 18 comprise respectively the cathode 20,;plate 22 and grid 24 and the cathode 26, plate 28 and grid 30. I

The primary windingv of therepeating coil or output transformer 31 is divided intotwo coils 33 and 35. The secondary winding 37 is. connected to the load circuit L by means of the conductors 39 and v41. "The primary winding of the repeating coilor output transformer 32 in amplifier 2 is divided into two coils 34 and 36. The secondary winding 38 is connected in parallel with the secondary winding 37 of transformer 31 to the load circuit L by means of conductors 10 and 42.

The cathodes or heated filaments 19, 25, 20 and 26 of the electron discharge devices 15,17, 16 and 18 respectively are heated by current from the alternating current source 50. A transformer 51 having preferably a primary winding 52 and two separate and unconnected secondary windings 53 and 5a is employed between the AC source 50 and the cathodes or filaments of the electron discharge devices. The cathodes or filaments 19 and 25 of the electron'discharge devices 15 and 17, which are included in the repeater or amplifier 1, are connected in series with each other by means of the conductor 55 and y the series connection of these two filaments is preferably directly connected to the wind ing 53 of transformer 51. The cathodes or filaments 20 and 26 of the electron discharge devices 16 and 18, which are included in the repeater or amplifier 2, are connected in series'with each other by means of the conductor 56 and the series connection of these two filaments 18 preferably directly connected to the winding 5-il of thetransformer51.

The filaments 2O an'd'26 are connected to the 'W1I1d11'lgS 54: so that when the filanient or cathode 19 of the thermionic discharge device 15 is positive with respect to the filament orcathode .25 of the thermionic discharge device 17,.the filament or cathode 26 of the thermionic discharge device 18 will also be positive with respect to the filament or cathode 20 of the thermionic discharge device 16. A suitable source of anode or plate potent1al61 1s connected in thecommon output input secondary windings;

way of the conductors ll and 13 and 12 and 1 1 are received in the primary windings 3 and 4; of the repeating coils 5 and6 respectively. The currents in the p rimarywinding 3 of repeating coil 5 produce voltage waves inthe windings 7 and: 9 of'the secondary winding thereof in the input circuit of:the

thermionic amplifiers 15- .aiid 17 .These waves will he amplified and repeatedin the windings 33 and 35of the output transformer 31. The details of the operationof a pushpull amplifier system are wellknown in th e art and are described, for example, in patent to'E. H. Colpitts, No. 1,123,292,.is: sued Februaryv16, 1915/ Ina similar manher the waves in the primary winding 4 of the input transformer 6 are amplified and repeatedin the windings 3 1. and '36 of the output transformer 32.

i As the secondary windings 37 and 3 8 of the transformers 31 and 32 respectively are connected in paralleltothevload circuitL the signaltransmitted through both the am: plifiers 1 and 2 will be impressed on the load circuit L. V

The use of alternating current to heat the filaments changes the potential difference between the cathodes 19, 25, 20 and .26 andtheil. associated control electrodes 23, 29, 24;;and 30' respectively as the voltage varies from its maximuni value in one, direction tlirougih zero to its maximum value in the other direction. These variations, unless neutralized or compensated. for, willbe repeated inthe out;- put circuits of the'amplifiers'. 1 and 2' and I they will be superimposed onthe signal currents due to the alternating filament supply which currents will not be in phase opposition.

The winding 54 of the transformer 51 is connected to the cathodes 20 and 26 so that the cathode 26 is positive with respect to the cathode 20 during the same time interval that cathode 19 is positive with respect to cathode 25. There will then be produced across the transformer winding 37 a filament current noise component equal and opposite to that produced across the transformer winding 38. Since these two transformer windings 37 and 38 are connected in parallel to the load L these two equal and opposite hum components will neutralize each other in the final output circuit.

Fig. 1A shows an alternate method of connecting the two push-pull amplifiers to the source of voltage S and to the load circuit L. The primary windings 3 and 4 of the transformers 5 and 6 are connected together by means of the conductor and the series connection of the windings 3 and 4 are con nected to the source of voltage S by means of conductors 71 and 72. The secondary windings 37 and 38 of the output transformers 31 and 32 are connected together by means of conductor 73 and the series connection of the windings 37 and 38 are connected to the load circuit L by means of the conductors 74 and? 5.

The signal currents from the voltage source S are impressed on the series connection of the primary windings 3 and 4 of the input transformers and repeated and amplified by the thermionic discharge devices. They are impressed on the load circuit L by means of the series connection of the secondary windings 37 and 38 of the output transformers.

The hum components of the alternating current supplied to the cathodes produce equal and opposite voltages in the output windings 37 and 38 of the output transformers 31 and 32 respectively, which voltages annul each other so that the resulting AC hum voltage applied to the load circuit L at all times approaches zero.

In Fig. 1-B is shown another scheme of connections similar in general to that of Fig. 1 but in which the input transformers 5 and 6 have been replaced by a single input transformer 76 and the output transformers 31 and 32 have been replaced by a single output transformer 77. The inputtransformer 76 comprises a core on which are mounted a pri mary winding 78 and four secondary'windings 79, 81, 80 and 82. These windings 79, 81, 80 and 82 correspond to the windings 7 and 9 of transformer 5 and windings 8 and 10 of transformer 6 respectively. They are connected to the thermionic discharge devices in the same manner as the corresponding windings of transformers 5 and 6. The output transformer 77 comprises a core on which are wound a winding 83 adapted to be connected to the load circuit L and four other windings 85, 87, 86 and 88. These four windings 85, 87, 86 and 88 correspond to the windings of transformers 31 and 32. The method of M operation of this circuit is identical with that described above for Fig. 1--A.

Referring to Fig. 2, the primary Winding 101 of a push-pull input transformer or re- I,

peating coil 102 is connected to the voltage source S. The secondary winding of the transformer or repeating coil 102 is divided into two coils 103 and 104. Four electron discharge devices 105, 106, 107 and 108 are included in the amplifier circuit. The electron discharge device comprises a heated filament or cathode 109, the anode or plate 110 and the control electrode or grid 111; the electron discharge device 106 comprises the heated filament or cathode 112, the anode or plate 113 and the control electrode 114; the electron discharge device 107 comprises the cathode 115, plate 116 and grid 117 and the electron discharge device 108 comprises the cathode 118, plate 119 and grid 120.

The terminal 127 of the coil 103 is connected by means of the conductor 129 to the grids 111 and 117 of the thermionic discharge devices 105 and 107 respectively. The terminal 128 of the coil 104 is connected by means of conductor 130 to the grids 114 and 120 of the thermionic discharge devices 106 and 108 respectively.

The primary winding of the repeating coil or output transformer 121 is divided into two coils 123 and 124. The secondary winding 125 is connected to the load circuit L. The anodes or plates 110 and 116 of the thermionic discharge devices 105 and 107 are connected together and to the terminal 131 of coil 123 and the anodes or plates 113 and 119 of the thermionic discharge devices 106 and 108 are connected to the terminal 132 of coil 124.

The cathodes or heated filaments 109, 112, 115 and 118 of the electron discharge devices 105, 106, 107 and 108 respectively are heated by current from the alternating current source 150. A transformer 151 having'a primary winding 152 and preferably two separate and unconnected secondary windings and 154 is employed between the AC source and the cathodes or filaments of the electron discharge devices. The cathodes or filaments 115 and 118 of the electron discharge devices 107 and 108 are connected in series with each other by means of the conductor 134 and the series connection of these two filaments is preferably directly con nected to the winding 153 of transformer Ti ice with respect to the filament or cathode 115 of thermionic discharge device 107 the filament or cathode 109 of the thermionic discharge device 105 will also be positive with respect to the filament 112 "of the thermionic discharge device 106.

A suitable source of anode or plate potential 135 is connected in the common output circuit of the thermionic discharge devices by means of conductor 136 from the connection of windings 123 and 124 and by means of the conductor 140 to the conductors 133 and 134 which connect the filaments 109 and 112 in series and the filaments 115 and 118 in series. A suitable source of biasing potential 137 is connected in the common input circuit of the thermionic discharge devices by means of the conductor 138 from the connection of windings 103 and 104 and by means of the conductor 140 tothe conductor 133' connecting the filaments 109 and 112 in series and the conductor 134 connecting the filaments 115 and 118 in series.

The operation of the system is as follows: Telephonic currents or other electric current waves incoming from the source S are received in theiprimary winding 101 of the repeating coil 102. The' currents in the primary winding 101 produce voltage waves in the windings 103 and 104 of the secondary winding thereof in the input circuits of the thermionic amplifiers 105 and 107' and 106 and 108 respectively. These waves will be amplified and repeated in the windings 123 and 124 of the output transformer 131 and transmitted to the load L. The details of the operation of a push-pull amplifier system have been referred to above in connection with Fig. 1.

The use of alternating current to heat the filaments changes the potential difference between the cathodes 1'09, 112, 115 and 118 and their associated control electrodes 111, 114, 117 and 120 respectively as the voltage varies from' its maximum value in one direction through zero to its maximum value in the other direction. At any given time, except of course at the moment when the waves in the secondary windings of transformer 151 are passing through zero, the voltage amplitude impressed across one filament say 109 of thermionic discharge device 105 will be positive with respect to the potential impressed across the filament 112 of thermionic discharge device 106.

The winding 154 of the transformer 151 is connected to the cathodes 109 and 112 so that the cathode 109 is positive with respect to the cathode 112 during the same time interval that cathode 118 is positive with respect to cathode 115. As the cathode 109 of the thermionic discharge device 105 is always positive when the cathode 115 of the ther mionic discharge device 107 is negative and vice versa the currents through the cathode 109 are always in phase opposition to the cur rents through the cathode 115 and the average voltage diff'erence between the cathodes 109 and 115 and the grids 111 and 117 will be unaffected by the current changes in the cathodes 109 and 115. There will, therefore, be no currents in the output circuits of the thermionic discharge devices 105 and 107 due to the alternating heating currents in the oathode circuits. In like manner the average voltage difference between the cathodes 112 and 118 of the thermionic discharge devices 106 and 108 and the grids 114 and 120 will be unaffected by the current changes inthe cathodes 112 and 118.

Fig. 3 is a modification of the amplifier shown in Fig. 2. It is the same as Fig. 2 except for the connections from the AC supply 150 to the cathodes of the thermionic discharge device. The cathodes 109 and 115 of the thermionic discharge devices 105 and 107 respectively are connected in series with each other by means of conductor 141 and the series connection of these two cathodes is preferably directly connected to the winding 153 J of the transformer 151. The cathodes 112 and 118 of the thermionic discharge devices 106 and 108 are connected in series with each other by means of conductor 142 and the series connection of these two cathodes is preferably directly connected to the winding 154 of the transformer 151. The filaments or cathodes 112 and 118 are connected to the winding 154 of the transformer 151 so that the cathode 112 is positive with respect to the cathode 118 when the cathode 115 of the thermionic discharge device 107 is positive with respect to the cathode 109 or the thermionic discharge device 105. The source of anode or plate potential 135 and the source of biasing potential 137 areconnected by means of conductor 140 to the conductors 141 and 142 which connect together the cathodes 109 and 115 and the cathodes 112 and 118.. This circuit operates, to eliminate the AC hum in the same manner as the circuit shown in Fig. 2. y I

Although these amplifiers have been shown asaudio, frequency amplifiers it is to be understood that this methodof neutralizing hum components introduced into the filament heating circuits is applicable to radio frequency amplifiers as well, the invention being adaptable to radio receivers and the like.

Accordingly the scope of the invention is to be limited only by the appended claims.

lVhat is claimed is:

1. In an electric wave amplifying system comprising divided input and divided output circuits employing a plurality of electron discharge devices, each having an anode, a cathode and a control electrode, the cathode of each of said discharge devices connected in series with the cathode of another of said discharge devices, two of said discharge devices having' their control electrodes connected in parallel to one side of said divided input circuit and their anodes connected in parallel to one side of said divided output circuit, two other of said discharge devices having their control electrodes connected in parallel to the other side of said divided input circuit and their anodes connected 1n parallel to the other side of said divided output circuit, a source of alternating current for heating the cathodes of said devices, and means comprising a transformer having two separate secondary windings between said source and said cathodes, each of said secondary windings being included in the series circuit of the cathodes of two of said discharge devices.

2. In an electric .wave amplifying system comprising divided input and divided output circuits employing a plurality of electron discharge devices, each having an anode, a cathode and a control electrode, two of said discharge devices having their control electrodes connected in parallel to one side of said divided input circuit and their anodes connected in parallel to one side of said divided output circuit, two other of said discharge devices having their control electrodes connected in parallel to the other side of said divided input circuit and their anodes connected in parallel to the other side of said divided output circuit, the cathode of one of said first two devices being connected in series with the cathode of one of said second two devices and with a secondary winding of a transformer, the primary winding of said transformer being connected to a source of alternating current to supply heating energy to the cathodes of said devices, and the cathode of the other of said first two devices being connected in series with the cathode of the remaining of said second two devices and with a second separate secondary winding of said transformer and a connection from the point of division of said input circuit to the point of division of said output circuit and to the direct series connections of said cathodes, external of said secondary windings.

3. A push-pull amplifier comprising two electron discharge devices, each of said devices having a cathode, an anode and an impedance control element, the cathodes of said two devices being connected in series to a secondary winding of a transformer, said secondary winding being a series element in the circuit socompleted, the primary winding of said transformer being connected to a source of alternating current to supply heating energy to said cathodes, and a common impedance control element connection path from the divided input of said push-pull amplifier to the divided output of said push-pull amplifier and to the direct series connection of said cathodes and external to said secondary windin 4. In an amplifying system, two electron discharge devices, each having a cathode, an anode and an impedance control element, the input circuits of said devices connected efiectively in parallel and the output circuits of said devices connected effectively in parallel, a source of alternating current to supply heating energy to the cathodes of said tubes, a transformer having a primary winding associated with said source and a secondary winding, the cathodes of said tubes being connected in series with each other and with said secondary winding, and a common impedance control element connection path leading to a point in the cathode heating circuitbetween said cathodes and'external to said secondary winding. V

5. In an amplifying system comprising divided input and divided output circuits employing a plurality of electron discharge devices, each having an anode, a cathode and a control electrode, two of said discharge devices having their control electrodes connected in parallel to one side of said divided input circuit, their anodes connected in parallel to one side of said divided output circuit and their cathodes connected in series with each other and'with asecondary winding of a transformer, the primary winding ofsaid transformer being connected to a source of alternating current for heating said cathodes, two other of said discharge devices having their control electrodes connected in parallel to the other side of said divided input circuit, their anodes connected in parallel to the other side of said divided output circuit and their cathodes connected in series with each other and with a second secondary winding of said transfo-rmer,'and'a connection from the point of division of said input circuit to the point of division of said output circuit and a common direct connection from said first mentioned connection to bothof'the direct series connections of said cathodes, (external to said secondary windings).

In witness whereof, I hereunto subscribe my name this 23 day of December, 1929.

JOHN L. REYNOLDS. 

